Account is assigned automatically

What causes this issue?

For this goods movement, the system makes a posting to an account
that is determined automatically. Manual entry of the G/L account is
not supported for the movement type.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Press ENTER and continue.
After you have posted the movement, you can display the document.
From the overview screen or the detail screen of an item, you can
display the accounting document and thus the G/L accounts to which
postings were made as a result of the movement.

Error message extract from SAP system. Copyright SAP SE.